1. Field of the Invention
The invention relates to substrates and methods for fabricating the same, and more particularly to epitaxial ZnGa2O4 substrates and methods for fabricating the same.
2. Description of the Related Art
Flat panel display devices, such as field emission displays (FEDs), plasma display panels (PDPs), and thin-film electroluminescent devices, require highly efficient phosphor material. Oxide phosphors offer potential advantages because of their superior stability under electron bombardment and excellent luminescent property.
ZnGa2O4 are oxide phosphors attractive for both cathodoluminescent and electroluminescent applications. ZnGa2O4 possesses a cubic spinel crystal structure and wide energy band gap of about 4.4 to 5.0 e.V. This material exhibits an intense green luminescence when doped with Mn and blue luminescence without doping via a transition of a self-activated center. It has been suggested that by doping with various activators, including Mn2+, Eu3+ and Ce3+ ZnGa2O4 phosphors can attain full color luminescence. ZnGa2O4 is also an interesting ultraviolet-transparent conductive oxide as moderate conductivity can be induced by annealing under a reducing atmosphere at high temperature.
There have been several studies on ZnGa2O4. For example, Yong Eui Lee et al. disclose “Enhanced ultraviolet photoconductivity in semiconducting ZnGa2O4 thin films” in JOURNAL OF APPLIED PHYSICS in volume 90, number 8. Yong Eui Lee et al. disclose “Blue photoluminescence in ZnGa2O4 thin film phosphors” in JOURNAL OF APPLIED PHYSICS in volume 89, number 3. Yong Eui Lee et al. disclose “Enhanced photoluminescence in epitaxial ZnGa2O4:Mn thin film phosphors using pulsed laser deposition” in APPLIED PHYSICS LETTER in volume 74, number 21.
Although numerous studies involve epitaxial ZnGa2O4 film, ZnGa2O4 can currently only be grown epitaxially on MgO substrates at high temperature. Unfortunately, MgO substrate is not only expensive, but also easily hydrolyzed in a moist ambient. Thus, devices and methods for overcoming obstacles to epitaxial growth of ZnGa2O4 film are desirable.